We consider the minimal lattice-based HP model for protein folding [1]}, in which
the protein is represented by a self-avoiding chain of hydrophobic (H) or polar (P) beads
on a lattice. Two beads are said to be
in contact if they are nearest neighbors on the lattice but not along the chain. A given chain
configuration is assigned an energy defined as \(E_{\text{HP}}=-N_{\text{HH}}\) , where \(N_{\text{HH}}\)  is the number of
HH contacts [1]}. With this choice of energy, low-energy configurations tend
to exhibit a hydrophobic core of H beads. Despite the simplicity of the model, there are
HP sequences with a unique ground state, and therefore a well-defined structure. In particular, on a
2D square lattice, it is known from exhaustive enumerations that about 2% of all HP sequences
with \(\le \) 30 beads have a unique ground state [3]}, [4]}.
